Description


I find some empty parts after background merge. These parts are old enough to be deleted permanently. Why does it still exists?

Question1: Does it work as expect?


I have read the source code about background merge logic, but not found logic to delete it.

Question2: Can it cause "too many parts" problem?

Maybe, it can exceeds the parts amount limitation max_parts_in_total.

Now, i can avoid this problem by the following two steps:

• Wait for background merge or trigger merge manually by "OPTIMIZE xxx"
 to ensure that only one part for one outdated partition.
• Drop outdated partition by "ALTER TABLE table_name DROP PARTITION XXX".

Question3: Why not remote it permanently?

Why not do this? Are there any other considerations?

CH version 19.16.20.1.